DATACMNS-867 - Use Optional in AbstractQueryCreator to handle ParameterAccessor presence.

AbstractQueryCreator now requires constructor arguments and no longer permits passing null values for ParameterAccessor. ParameterAccessor is wrapped in Optional to correctly handle its presence and absence without dealing with null values.

src/main/java/org/springframework/data/repository/query/parser/AbstractQueryCreator.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2008-2013 the original author or authors.
+ * Copyright 2008-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,6 +16,7 @@
 package org.springframework.data.repository.query.parser;
 
 import java.util.Iterator;
+import java.util.Optional;
 
 import org.springframework.data.domain.Sort;
 import org.springframework.data.repository.query.ParameterAccessor;
@@ -25,75 +26,81 @@ import org.springframework.util.Assert;
 
 /**
  * Base class for query creators that create criteria based queries from a {@link PartTree}.
- * 
- * @param T the actual query type to be created
- * @param S the intermediate criteria type
+ *
+ * @param <T> the actual query type to be created
+ * @param <S> the intermediate criteria type
  * @author Oliver Gierke
+ * @author Mark Paluch
  */
 public abstract class AbstractQueryCreator<T, S> {
 
-	private final ParameterAccessor parameters;
+	private final Optional<ParameterAccessor> parameters;
 	private final PartTree tree;
 
+	/**
+	 * Creates a new {@link AbstractQueryCreator} for the given {@link PartTree}. This will cause {@literal null} be
+	 * handed for the {@link Iterator} in the callback methods.
+	 *
+	 * @param tree must not be {@literal null}.
+	 * @since 2.0
+	 */
+	public AbstractQueryCreator(PartTree tree) {
+		this(tree, Optional.empty());
+	}
+
 	/**
 	 * Creates a new {@link AbstractQueryCreator} for the given {@link PartTree} and {@link ParametersParameterAccessor}.
 	 * The latter is used to hand actual parameter values into the callback methods as well as to apply dynamic sorting
 	 * via a {@link Sort} parameter.
-	 * 
+	 *
 	 * @param tree must not be {@literal null}.
-	 * @param parameters can be {@literal null}.
+	 * @param parameters must not be {@literal null}.
 	 */
 	public AbstractQueryCreator(PartTree tree, ParameterAccessor parameters) {
+		this(tree, Optional.of(parameters));
+	}
+
+	private AbstractQueryCreator(PartTree tree, Optional<ParameterAccessor> parameters) {
 
 		Assert.notNull(tree, "PartTree must not be null");
+		Assert.notNull(parameters, "ParameterAccessor must not be null");
 
 		this.tree = tree;
 		this.parameters = parameters;
 	}
 
-	/**
-	 * Creates a new {@link AbstractQueryCreator} for the given {@link PartTree}. This will cause {@literal null} be
-	 * handed for the {@link Iterator} in the callback methods.
-	 * 
-	 * @param tree must not be {@literal null}.
-	 */
-	public AbstractQueryCreator(PartTree tree) {
-
-		this(tree, null);
-	}
-
 	/**
 	 * Creates the actual query object.
-	 * 
+	 *
 	 * @return
 	 */
 	public T createQuery() {
-		return createQuery(parameters.getSort());
+		return createQuery(parameters.map(ParameterAccessor::getSort) //
+				.orElse(Sort.unsorted()));
 	}
 
 	/**
 	 * Creates the actual query object applying the given {@link Sort} parameter. Use this method in case you haven't
 	 * provided a {@link ParameterAccessor} in the first place but want to apply dynamic sorting nevertheless.
-	 * 
+	 *
 	 * @param dynamicSort
 	 * @return
 	 */
 	public T createQuery(Sort dynamicSort) {
-
 		return complete(createCriteria(tree), tree.getSort().and(dynamicSort));
 	}
 
 	/**
 	 * Actual query building logic. Traverses the {@link PartTree} and invokes callback methods to delegate actual
 	 * criteria creation and concatenation.
-	 * 
+	 *
 	 * @param tree
 	 * @return
 	 */
 	private S createCriteria(PartTree tree) {
 
 		S base = null;
-		Iterator<Object> iterator = parameters == null ? null : parameters.iterator();
+		Iterator<Object> iterator = parameters.map(ParameterAccessor::iterator).orElse(null);
 
 		for (OrPart node : tree) {
 
@@ -112,7 +119,7 @@ public abstract class AbstractQueryCreator<T, S> {
 
 	/**
 	 * Creates a new atomic instance of the criteria object.
-	 * 
+	 *
 	 * @param part
 	 * @param iterator
 	 * @return
@@ -121,7 +128,7 @@ public abstract class AbstractQueryCreator<T, S> {
 
 	/**
 	 * Creates a new criteria object from the given part and and-concatenates it to the given base criteria.
-	 * 
+	 *
 	 * @param part
 	 * @param base will never be {@literal null}.
 	 * @param iterator
@@ -131,7 +138,7 @@ public abstract class AbstractQueryCreator<T, S> {
 
 	/**
 	 * Or-concatenates the given base criteria to the given new criteria.
-	 * 
+	 *
 	 * @param base
 	 * @param criteria
 	 * @return
@@ -140,7 +147,7 @@ public abstract class AbstractQueryCreator<T, S> {
 
 	/**
 	 * Actually creates the query object applying the given criteria object and {@link Sort} definition.
-	 * 
+	 *
 	 * @param criteria will never be {@literal null}.
 	 * @param sort might be {@literal null}.
 	 * @return